Full Disclosure: I make Raincoat and Fogtech.
Thank you for the longer term report. I would like to post it on my website if OK with you?
Your observations about Plexus and other cleaners on Raincoat are exactly in line with my experiments. So it is good to see those validated in the real world. It doesn't rain enough in California for me to test the longevity of Raincoat by riding.
Plexus is a very good cleaner and plastic polish, good enough to remove a portion of the Raincoat wax. So now I recommend a new coating when you clean your shield aggressively. Plain water or a light soap and water with limited rubbing don't seem to have much affect on the life of the Raincoat. But every manufacturer's shield is different so better to be safe.
I have also tried to apply Raincoat over shields cleaned by Plexus. A few riders said they were concerned that Raincoat would not stick with some Plexus left behind. Or that it might cause some vision defects. I did not see that. It worked just fine on my Arai, Shoei, HJC and Schuberth test shields that had a coating of Plexus.
Also, I have a report from the owner of Epicurean Riders that he puts Raincoat on all of his plastic, even his turn signals! He claims it keeps them cleaner much longer. Epicurean Riders Comment
One last comment. I am modifying the packaging to make it easier to save and get more uses from the contents of each pouch. I would estimate that you will be able to coat your shield about 30 to 50 times with a typical 5 pack. Also the instructions are changing to make Raincoat much easier to buff.